Magnetic Tunnel Junction Device and Method

ABSTRACT

In an embodiment, a device includes: a magnetoresistive random access memory (MRAM) array including MRAM cells arranged in rows and columns, where a first column of the columns includes: first bottom electrodes arranged along the first column; first magnetic tunnel junction (MTJ) stacks over the first bottom electrodes; a first shared electrode over each of the first MTJ stacks; second bottom electrodes arranged along the first column; second MTJ stacks over the second bottom electrodes; a second shared electrode over each of the second MTJ stacks; and a bit line electrically connected to the first shared electrode and the second shared electrode.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a divisional of U.S. patent application Ser. No.16/887,244, filed on May 29, 2020, entitled “Magnetic Tunnel JunctionDevice and Method,” which application is hereby incorporated herein byreference.

BACKGROUND

Semiconductor memories are used in integrated circuits for electronicapplications, including radios, televisions, cell phones, and personalcomputing devices, as examples. One type of semiconductor memory ismagnetoresistive random access memory (MRAM), which involves spinelectronics that combines semiconductor technology and magneticmaterials and devices. The spins of electrons, through their magneticmoments, are used to indicate bit values. A MRAM cell typically includesa magnetic tunnel junction (MTJ) stack, which includes two ferromagnetsseparated by a thin insulator.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a block diagram of a MRAM device, in accordance with someembodiments.

FIG. 2 is a cross-sectional view of a MRAM device, in accordance withsome embodiments.

FIGS. 3 through 23 are various views of intermediate stages in themanufacturing of an interconnect structure for a MRAM device, inaccordance with some embodiments.

FIGS. 24 and 25 are various views of a MRAM device, in accordance withsome embodiments.

FIGS. 26 through 40 are cross-sectional views of intermediate stages inthe manufacturing of an interconnect structure for a MRAM device, inaccordance with some other embodiments.

FIG. 41 is a cross-sectional view of a MRAM device, in accordance withsome other embodiments.

FIG. 42 is a cross-sectional view of a MRAM device, in accordance withsome other embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In accordance with some embodiments, a MRAM array is formed in aninterconnect structure, with the MRAM array including shared electrodesfor the MTJ stacks in the MRAM array. Specifically, electrodes areshared by multiple MTJ stacks along columns of the MRAM array, and areelectrically connected to a same bit line. Forming shared electrodes forthe MTJ stacks helps reduce the contact resistance to the MTJ stacks,and reduces the risk of damage to the MTJ stacks during the subsequentformation of overlying metallization layers. In accordance with someother embodiments, dielectric protective structures are formed aroundthe MRAM cells before formation of overlying metallization layers. Theprotective structures prevent etching of the MTJ stacks during thesubsequent formation of overlying metallization layers. By forming theshared electrodes and/or protective structures, damage to the MRAM cellsmay be avoided during processing, particularly when the MRAM array isformed in a higher level of the interconnect structure.

FIG. 1 is a block diagram of a MRAM device 50, in accordance with someembodiments. The MRAM device 50 includes a MRAM array 52, a row decoder54, and a column decoder 56. The MRAM array 52 includes MRAM cells 58arranged in rows and columns. The row decoder 54 may be, e.g., a staticCMOS decoder, a pseudo-NMOS decoder, or the like. During operation, therow decoder 54 selects desired MRAM cells 58 in a row of the MRAM array52 by activating the respective word line WL for the row. The columndecoder 56 may be, e.g., a static CMOS decoder, a pseudo-NMOS decoder,or the like, and may include writer drivers, sense amplifiers,combinations thereof, or the like. During operation, the column decoder56 selects bit lines BL for the desired MRAM cells 58 from columns ofthe MRAM array 52 in the selected row, and reads data from or writesdata to the selected MRAM cells 58 with the bit lines BL.

FIG. 2 is a cross-sectional view of the MRAM device 50, in accordancewith some embodiments. FIG. 2 is a simplified view, and some features(discussed below) are omitted for clarity of illustration. The MRAMdevice 50 includes a logic region 50L and a memory region 50M. Memorydevices (e.g., MRAMs) are formed in the memory region 50M and logicdevices (e.g., logic circuits) are formed in the logic region 50L. Forexample, the MRAM array 52 (see FIG. 1 ) can be formed in the memoryregion 50M, and the row decoder 54 and column decoder 56 (see FIG. 1 )can be formed in the logic region 50L. The logic region 50L may occupymost of the area of the MRAM device 50. For example, the logic region50L may occupy from 95% to 99% of the area of the MRAM device 50, withthe memory region 50M occupying the remaining area of the MRAM device50. The memory region 50M can be disposed at an edge of the logic region50L, or the logic region 50L can surround the memory region 50M.

The logic region 50L and memory region 50M are formed over a samesemiconductor substrate 60. The semiconductor substrate 60 may besilicon, doped or undoped, or an active layer of asemiconductor-on-insulator (SOI) substrate. The semiconductor substrate60 may include other semiconductor materials, such as germanium; acompound semiconductor including silicon carbide, gallium arsenic,gallium phosphide, gallium nitride, indium phosphide, indium arsenide,and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP,AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof.Other substrates, such as multilayered or gradient substrates, may alsobe used.

Devices 62 are formed at the active surface of the semiconductorsubstrate 60. The devices 62 may be active devices or passive devices.For example, the electrical components may be transistors, diodes,capacitors, resistors, or the like, formed by any suitable formationmethod. The devices 62 are interconnected to form the memory devices andlogic devices of the MRAM device 50. For example, some of the devices 62may be access transistors.

One or more inter-layer dielectric (ILD) layer(s) 64 are formed on thesemiconductor substrate 60, and electrically conductive features, suchas contact plugs 66, are formed electrically connected to the devices62. The ILD layer(s) 64 may be formed of any suitable dielectricmaterial, for example, a nitride such as silicon nitride; an oxide suchas silicon oxide, phosphosilicate glass (PSG), borosilicate glass (BSG),boron-doped phosphosilicate glass (BPSG), or the like; or the like. TheILD layer(s) may be formed by any acceptable deposition process, such asspin coating, physical vapor deposition (PVD), chemical vapor deposition(CVD), the like, or a combination thereof. The electrically conductivefeatures in the ILD layer(s) may be formed through any suitable process,such as deposition, damascene (e.g., single damascene, dual damascene,etc.), the like, or combinations thereof.

An interconnect structure 68 is formed over the semiconductor substrate60. The interconnect structure 68 interconnects the devices 62 to formintegrated circuits in each of the logic region 50L and memory region50M. The interconnect structure 68 includes multiple metallizationlayers M1-M6. Although six metallization layers are illustrated, itshould be appreciated that more or less metallization layers may beincluded. Each of the metallization layers M1-M6 includes metallizationpatterns in dielectric layers. The metallization patterns areelectrically coupled to the devices 62 of the semiconductor substrate60, and include, respectively, metal lines L1-L6 and metal vias V1-V6formed in one or more inter-metal dielectric (IMD) layers. Theinterconnect structure 68 may formed by a damascene process, such as asingle damascene process, a dual damascene process, or the like. In someembodiments, the contact plugs 66 are also part of the metallizationpatterns, such as part of the lowest layer of metal vias V1. FIG. 2 isalso labeled with some reference numerals that will be described furtherbelow.

The MRAM cells 58 are formed in the interconnect structure 68. The MRAMcells 58 can be formed in any of the metallization layers M1-M6, and areillustrated as being formed in an intermediate metallization layer M5.Each MRAM cell 58 includes a conductive via 72, a bottom electrode 74 onthe conductive via 72, a MTJ stack 76 on the bottom electrode 74, and atop electrode 78 on the MTJ stack 76. An additional IMD layer 80 can beformed around the MRAM cells 58, with the conductive via 72 extendingthrough the IMD layer 80. Spacers 82 can also be formed around the MRAMcells 58. The IMD layer 80 and/or spacers 82 surround and protect thecomponents of the MRAM cells 58. The resistance of an MTJ stack 76 isprogrammable, and can be changed between a high resistance (R_(ap)),which can signify a value such as a logic “1,” and a low resistance(R_(p)), which can signify a value such as a logic “0.” As such, a valuecan be written to a MRAM cell 58 by programming the resistance of theMTJ stack 76 with its corresponding access transistor, and the value canbe read from the MRAM cell 58 by measuring the resistance of the MTJstack 76 with the access transistor.

The MRAM cells 58 are electrically connected to the devices 62. Theconductive via 72 is physically and electrically coupled to anunderlying metallization pattern, such as to the metal lines L4 in theillustrated example. The top electrode 78 is physically and electricallycoupled to an overlying metallization pattern, such as to the metal viasV6 in the illustrated example. The MRAM cells 58 are arranged in a MRAMarray having rows and columns of memory. The metallization patternsinclude access lines (e.g., word lines and bit lines) for the MRAMarray. For example, the underlying metallization patterns can includeword lines disposed along the rows of the MRAM array and the overlyingmetallization patterns can include bit lines disposed along the columnsof the MRAM array.

FIGS. 3 through 23 are various views of intermediate stages in themanufacturing of an interconnect structure for the MRAM device 50, inaccordance with some embodiments. The interconnect structure includes aMRAM array of memory cells. As discussed further below, groups of thememory cells along the columns of the MRAM array share electrodes, whichallows the contact resistance to the memory cells to be decreased.

In FIG. 3 , a metallization layer (e.g., M4, see FIG. 2 ) of theinterconnect structure is formed. The metallization layer comprises anIMD layer 102 and conductive features 104 (which can correspond to themetal lines L4, see FIG. 2 ). The IMD layer 102 is formed over the ILDlayer(s) 64. The IMD layer 102 may be formed of any suitable dielectricmaterial, for example, a nitride such as silicon nitride; an oxide suchas silicon oxide, phosphosilicate glass (PSG), borosilicate glass (BSG),boron-doped phosphosilicate glass (BPSG), or the like; or the like. TheIMD layer 102 may be formed by any acceptable deposition process, suchas spin coating, physical vapor deposition (PVD), chemical vapordeposition (CVD), the like, or a combination thereof. The IMD layer 102may be a layer formed of a low-k dielectric material having a k-valuelower than about 3.0. The IMD layer 102 may be a layer formed of anextra-low-k (ELK) dielectric material having a k-value of less than 2.5.

Conductive features 104 are formed in the IMD layer 102, and areelectrically connected to the devices 62. In accordance with someembodiments, the conductive features 104 include diffusion barrierlayers and conductive material over the diffusion barrier layers.Openings are formed in the IMD layer 102 using, e.g., an etchingprocess. The openings expose underlying conductive features, such asunderlying metal vias. The diffusion barrier layers may be formed ofTaN, Ta, TiN, Ti, CoW, or the like, and may be formed in the openings bya deposition process such as atomic layer deposition (ALD) or the like.The conductive material may include copper, aluminum, tungsten, silver,and combinations thereof, or the like, and may be formed over thediffusion barrier layers in the openings by an electro-chemical platingprocess, CVD, ALD, PVD, the like, or a combination thereof. In anembodiment, the conductive material is copper, and the diffusion barrierlayers are thin barrier layers that prevent the copper from diffusinginto the IMD layer 102. After formation of the diffusion barrier layersand the conductive material, excess of the diffusion barrier layers andconductive material may be removed by, for example, a planarizationprocess such as a chemical mechanical polish (CMP) process. In someembodiments, the conductive features 104 are metal lines.

One or more etch stop layer(s) 106 are formed on the conductive features104 and IMD layer 102. The etch stop layer(s) 106 may be formed of adielectric material such as aluminum nitride, aluminum oxide, siliconoxide, silicon nitride, silicon oxynitride, silicon carbide, acombination thereof, or the like. The etch stop layer(s) 106 may beformed by chemical vapor deposition (CVD), physical vapor deposition(PVD), ALD, a spin-on-dielectric process, the like, or a combinationthereof. The etch stop layer(s) 106 may also be a composite layer formedof a plurality of dielectric layers. In this embodiment, the etch stoplayer(s) 106 comprise a first etch stop layer 106A and a second etchstop layer 106B over the first etch stop layer 106A. The first etch stoplayer 106A can be formed of a first dielectric material, such as siliconcarbide, and the second etch stop layer 106B can be formed of a seconddielectric material, such as aluminum oxide. The silicon carbide layeris used as a glue layer to improve adhesion between the aluminum oxidelayer and the IMD layer 102. The etch stop layer(s) 106 can be formed toa combined thickness in the range of about 30 Å to about 150 Å.

An IMD layer 108 is formed on the etch stop layer(s) 106. In someembodiments, the IMD layer 108 is formed of a tetraethyl orthosilicate(TEOS) oxide (e.g., silicon oxide deposited using, e.g., a chemicalvapor deposition (CVD) method with TEOS as a precursor). In someembodiments, the IMD layer 108 may be formed using PSG, BSG, BPSG,undoped silicate glass (USG), fluorosilicate glass (FSG), SiOCH,flowable oxide, a porous oxide, or the like, or combinations thereof.The IMD layer 108 may also be formed of a low-k dielectric material witha k value lower than about 3.0, for example. The IMD layer 108 can beformed to a thickness in the range of about 350 Å to about 550 Å.

Conductive vias 110 are formed extending through the IMD layer 108 andetch stop layer(s) 106. The conductive vias 110 can also be referred toas bottom vias. In some embodiments, the conductive vias 110 includeconductive regions 114 and conductive barrier layers 112 liningsidewalls and bottom surfaces of the conductive regions 114. Theconductive barrier layers 112 may be formed of titanium, titaniumnitride, tantalum, tantalum nitride, cobalt, a combination thereof, orthe like. The conductive regions 114 may be formed of metals such ascopper, aluminum, tungsten, cobalt, alloys thereof, or the like. Theformation of the conductive vias 110 may include etching the IMD layer108 and etch stop layer(s) 106 to form via openings, forming a blanketconductive barrier layer extending into the via openings, depositing ametallic material over the blanket conductive barrier layer, andperforming a planarization process, such as a CMP process or amechanical grinding process, to remove excess portions of the blanketconductive barrier layer and the metallic material.

One or more bottom electrode layer(s) 116 are formed on the conductivevias 110 and IMD layer 108. In some embodiments, the bottom electrodelayer(s) 116 are formed as blanket layers, and may be formed using CVD,physical vapor deposition (PVD), electro-chemical plating (ECP),electroless plating, or the like. The bottom electrode layer(s) 116 maybe formed of conductive materials such as Cu, Al, Ti, Ta, W, Pt, Ni, Cr,Ru, TiN, TaN, combinations thereof, multilayers thereof, or the like.For example, the bottom electrode layer(s) 116 can comprise a firstbottom electrode layer 116A and a second bottom electrode layer 116Bover the first bottom electrode layer 116A. The first bottom electrodelayer 116A can be formed of a first conductive material, such as TaN,and the second bottom electrode layer 116B can be formed of a secondconductive material, such as TiN. The bottom electrode layer(s) 116 canbe formed to a combined thickness in the range of about 20 Å to about150 Å.

In FIG. 4 , a MTJ film stack 118 is formed on the bottom electrodelayer(s) 116. The MTJ film stack 118 is a multilayer that includes ananti-ferromagnetic layer 118A, a pinned layer 118B over theanti-ferromagnetic layer 118A, a tunnel barrier layer 118C over thepinned layer 118B, and a free layer 118D over the tunnel barrier layer118C. The MTJ film stack 118 has an overall thickness in the range ofabout 200 Å to about 400 Å. Each layer of the MTJ film stack 118 may bedeposited using one or more deposition methods such as, CVD, PVD, ALD, acombination thereof, or the like.

The anti-ferromagnetic layer 118A may be formed of a metal alloyincluding manganese (Mn) and one or more other metal(s) such as platinum(Pt), iridium (Ir), rhodium (Rh), nickel (Ni), palladium (Pd), iron(Fe), osmium (Os), or the like. For example, the anti-ferromagneticlayer 118A can be formed of PtMn, IrMn, RhMn, NiMn, PdPtMn, FeMn, OsMn,or the like. The anti-ferromagnetic layer 118A may have a thickness inthe range of about 50 Å to about 200 Å.

The pinned layer 118B may be formed of a ferromagnetic material with agreater coercivity field than the free layer 118D, such as cobalt iron(CoFe), cobalt iron boron (CoFeB), a combination thereof, or the like.The pinned layer 118B may have a thickness in the range of about 50 Å toabout 100 Å. In some embodiments, the pinned layer 118B has a syntheticferromagnetic (SFM) structure, in which the coupling between magneticlayers is ferromagnetic coupling. The pinned layer 118B may also adopt asynthetic antiferromagnetic (SAF) structure including a plurality ofmagnetic metal layers separated by a plurality of non-magnetic spacerlayers. The magnetic metal layers may be formed of Co, Fe, Ni, or thelike. The non-magnetic spacer layers may be formed of Cu, Ru, Ir, Pt, W,Ta, Mg, or the like. For example, the pinned layer 118B may have a Colayer and repeated (Pt/Co)_(x) layers over the Co layer, with xrepresenting repeating number that can be any integer equal to orgreater than 1, such as 20.

The tunnel barrier layer 118C may be formed of a dielectric material,such as MgO, AlO, AlN, a combination thereof, or the like. The tunnelbarrier layer 118C may have a thickness in the range of about 0.5 nm toabout 3 nm. The tunnel barrier layer 118C is thicker than the otherlayers of the MTJ film stack 118.

The free layer 118D may be formed of a ferromagnetic material such asCoFe, NiFe, CoFeB, CoFeBW, a combination thereof, or the like. The freelayer 118D may also adopt a synthetic ferromagnetic structure, which issimilar to a SAF structure, with the thickness of the non-magneticspacer layers adjusted to achieve the ferromagnetic coupling between theseparated magnetic metals, e.g., causing the magnetic moment to becoupled in the same direction. The magnetic moment of the free layer118D is programmable, and the resistances of the resulting MTJ stacks isaccordingly programmable. Specifically, the resistances of the resultingMTJ stacks can be changed between a high resistance (R_(ap)) and a lowresistance (R_(p)) based on the programmed magnetic moment of the freelayer 118D. As such, the resulting MTJ stacks can also be referred to asprogrammable resistance elements or programmable resistors. Thethickness of the tunnel barrier layer 118C contributes to the R_(ap) andthe R_(p) of the resulting MTJ stacks.

It should be appreciated that the materials and the structure of the MTJfilm stack 118 may have many variations, which are also within the scopeof the present disclosure. For example, the layers 118A, 118B, 118C, and118D may be formed in an order inversed from that described above.Accordingly, the free layer 118D may be the bottom layer of the MTJ filmstack 118, and the anti-ferromagnetic layer 118A may be the top layer ofthe MTJ film stack 118.

A top electrode layer 120 is formed on the MTJ film stack 118. In someembodiments, the top electrode layer 120 is formed as a blanket layer,and may be formed using CVD, PVD, ECP, electroless plating, or the like.The material of the top electrode layer 120 may include metals such astitanium, tantalum, tungsten, aluminum, copper, alloys thereof, or thelike. For example, the top electrode layer 120 can be formed of TiN, Ta,TaN, Ti, Ru, W, WC, Ru, multi-layers thereof, or the like. In someembodiments, the top electrode layer 120 is formed of titanium nitride.In some embodiments, the top electrode layer 120 has a thickness in therange of about 400 Å to about 1500 Å. In some embodiments, the thicknessof the top electrode layer 120 is greater than the combined thickness ofthe bottom electrode layer(s) 116. The top electrode layer 120 is usedas a hard mask in the subsequent patterning of the MTJ film stack 118.

In FIG. 5 , one or more masks are formed over the top electrode layer120. The masks will be used to simultaneously pattern the various layersand form MRAM cells. In some embodiments, the one or more masks maycomprise one or more hard masks, a tri-layer mask, a combinationthereof, or the like. For example, a hard mask layer 126 can be formedover the top electrode layer 120 and a photosensitive mask 128 can beformed over the hard mask layer 126. In some embodiments, the hard masklayer 126 is formed of an oxide such as titanium oxide, silicon oxide, acombination thereof, or the like. The photosensitive mask 128 may be aphotoresist, such as a single-layer photoresist, a bi-layer photoresist,a tri-layer photoresist, or the like. The photosensitive mask 128 isformed in the memory region 50M, with the pattern of the photosensitivemask 128 corresponding to the pattern of the subsequently formed MRAMcells.

In FIG. 6 , the photosensitive mask 128 is used as an etching mask toetch and pattern the hard mask layer 126. The patterned hard mask layer126 is then used as etching mask to etch and pattern the top electrodelayer 120, MTJ film stack 118, and bottom electrode layer(s) 116. Thepatterning may include one or more etching processes, and can formrecesses 130 in the IMD layer 108. The etching method may include aplasma etching method, such as ion beam etching (IBE). IBE offers a highlevel of precision (e.g., high anisotropism), which can help control theprofile of the resulting MRAM cells. The etching may be implementedusing glow discharge plasma (GDP), capacitive coupled plasma (CCP),inductively coupled plasma (ICP), or the like. The photosensitive mask128 and hard mask layer 126 may be consumed in the etching process, ormay be removed after the etching process.

The etching process forms bottom electrodes 132, MTJ stacks 134, and topelectrodes 136, which together form MRAM cells 58. Each MRAM cell 58includes a bottom electrode 132, a MTJ stack 134, and a top electrode136. The bottom electrodes 132 comprise remaining portions of the bottomelectrode layer(s) 116. The MTJ stacks 134 comprise remaining portionsof the MTJ film stack 118. The top electrodes 136 comprise remainingportions of the top electrode layer 120. In some embodiment, the etchingprocess partially etches the IMD layer 108 and conductive vias 110. Insuch embodiments, the remaining portions of the IMD layer 108 havesloped sidewalls, and have trapezoidal shapes in the illustratedcross-section. After the etching process, the remaining portions of theIMD layer 108 in the logic region 50L can have a thickness in the rangeof about 30 Å to about 300 Å. The MTJ stacks 134 and bottom electrodes132 also have sloped sidewalls, and have trapezoidal shapes in theillustrated cross-section.

In FIG. 7 , spacers 140 are formed on the sidewalls of the MRAM cells58. The spacers 140 surround and protect the components of the MRAMcells 58. The spacers 140 may be formed of an oxide (e.g., siliconoxide, aluminum oxide, etc.), a nitride (e.g., silicon nitride, aluminumnitride, etc.), a carbide (e.g., silicon carbide), combinations thereof(e.g., silicon oxynitride, silicon carbonitride, etc.), multilayersthereof, or the like.

In an embodiment where the spacers 140 comprise a multilayer, thespacers 140 comprise passivation layers 142 and 144 and an oxide layer146. As an example to form the spacers 140, the passivation layer 142can be blanket formed over the MRAM cells 58 and in the recesses 130(see FIG. 6 ). In some embodiments, the passivation layer 142 maycomprise silicon oxide, silicon nitride, silicon oxynitride, siliconcarbide, silicon carbonitride, a combination thereof, or the like, andmay be formed using CVD, plasma-enhanced chemical vapor deposition(PECVD), ALD, plasma-enhanced atomic layer deposition (PEALD), PVD, acombination thereof, or the like. In some embodiments, the passivationlayer 142 may reduce or prevent moisture (e.g., H₂O) diffusion into theMRAM cells 58 during subsequent processing. The passivation layer 142 isthen patterned to expose portions of the top electrodes 136. In someembodiments, the patterning is a dry etching process, such as ananisotropic etching process. The patterning removes horizontal portionsof the passivation layer 142. Subsequently, another passivation layer144 is formed over the passivation layer 142. In some embodiments, thepassivation layer 144 is formed of one of the candidate materials andmethods for the passivation layer 142, but is formed of a differentmaterial than the passivation layer 142. For example, the passivationlayer 142 can be formed of an oxide, e.g., silicon oxide, and thepassivation layer 144 can be formed of a nitride, e.g., silicon nitride.The oxide layer 146 is then formed over the passivation layer 144. Insome embodiments, the oxide layer 146 may comprise silicon oxide, or thelike, and may be formed using CVD, PECVD, ALD, PEALD, a combinationthereof, or the like. Subsequently, one or more dry etching processesare performed to etch the passivation layer 144 and the oxide layer 146and to expose portions of the top electrodes 136. In some embodiments,the one or more dry etching processes are anisotropic etching processesand remove horizontal portions of the oxide layer 146. The remainingportions of the passivation layer 142, the passivation layer 144, andthe oxide layer 146 form the spacers 140. The IMD layer 108 in the logicregion 50L is exposed after the spacers 140 are patterned.

In FIG. 8 , an etch stop layer 148 is formed over exposed portions ofthe spacers 140, top electrodes 136, and IMD layer 108. An IMD layer 150is then formed on the etch stop layer 148. The etch stop layer 148 canbe formed of a dielectric material such as aluminum nitride, aluminumoxide, silicon carbide, silicon carbonitride, a combination thereof,multilayers thereof, or the like. In some embodiments, the IMD layer 150is formed using similar materials and methods as the IMD layer 108. Insome embodiments, the etch stop layer 148 is formed of aluminum nitrideand the IMD layer 150 is formed of silicon oxide. Aluminum nitride andsilicon oxide have a high selectivity relative an etching process thatwill be used to pattern the IMD layer 150 (discussed further below). TheIMD layer 150 is formed to a thickness in the range of about 1200 Å toabout 1600 Å. Due to pattern loading, portions of the IMD layer 150 inthe memory region 50M can extend above portions of the IMD layer 150 inthe logic region 50L. The IMD layer 150 is formed to a sufficientthickness that the portions of the IMD layer 150 in the logic region 50Lhave a greater thickness than the MRAM cells 58.

In FIG. 9 , a planarization process is performed to planarize the IMDlayer 150. The planarization process can be a CMP process, a mechanicalgrinding process, or the like. The MRAM cells 58 remain buried after theplanarization process, and portions of the IMD layer 150 in the logicregion 50L and the memory region 50M share a planar topmost surfaceafter the planarization process.

In FIG. 10 , a hard mask 152 is formed on the planar topmost surface ofthe IMD layer 150. The hard mask 152 may comprise a dielectric materialsuch as silicon oxide, silicon nitride, titanium oxide, BSG, BPSG, USG,FSG, SiOCH, flowable oxide, a porous oxide, or the like; a conductivematerial such as titanium, tantalum, tungsten, alloys thereof, or thelike; multilayers thereof; or the like. For example, the hard mask 152can include a silicon carbide layer and a titanium nitride layer formedon the silicon carbide layer, with the titanium nitride layer having athickness in the range of about 200 Å to about 400 Å, and the siliconcarbide layer having a thickness in the range of about 50 Å to about 150Å. The silicon carbide layer is used as a glue layer to improve adhesionbetween the titanium nitride layer and the IMD layer 150. After themasking material of the hard mask 152 is formed, a patterning process isperformed, with remaining portions of the masking material forming thehard mask 152. The patterning can be a dry etching process, such as ananisotropic etching process, using a photoresist as an etching mask. Thephotoresist can be a single-layer photoresist, a bi-layer photoresist, atri-layer photoresist, or the like. The resulting hard mask 152 hasopenings 154, exposing underlying portions of the IMD layer 150.

FIG. 11 is a top-down view of the MRAM device 50 after formation of thehard mask 152. As discussed further below, the hard mask 152 will beused to pattern openings 156 (see FIG. 12 ) in the IMD layer 150,exposing the underlying MRAM cells 58. The openings 154 in the hard mask152 are each disposed over several MRAM cells 58 along columns of theMRAM array 52 (see FIG. 1 ). As such, each opening 156 (see FIG. 12 )subsequently formed in the IMD layer 150 will expose multiple MRAM cells58 along columns of the resulting MRAM array 52.

Each opening 154 will be used to expose the same quantity of MRAM cells58 in the memory region 50M. The openings 154 in the hard mask 152 areof uniform dimensions, e.g., uniform widths W₁ and uniform lengths L₁.The widths W₁ of the openings 154 are can be in the range of about 250 Åto about 450 Å, and are larger than diameters D₁ of the MRAM cells 58,such as the diameters of the top electrodes 136. The diameter D₁ can bein the range of about 300 Å to about 400 Å. The lengths L1 can be in therange of about 1400 Å to about 50 μm, and are large enough to spanseveral MRAM cells 58. In the illustrated embodiment, the openings 154fully expose MRAM cells 58 in the center region of the openings 154, andpartially expose MRAM cells 58 at the end regions of the openings 154.Specifically, the openings 154 can overlap with MRAM cells 58 at the endregions of the openings 154 by a distance D₂, which can be less thanabout 100 Å.

FIG. 11 further illustrates reference cross-sections that are used inlater figures. Cross-section A-A is along a column of the MRAM array 52(see FIG. 1 ) and in a direction of, for example, a bit line for theMRAM array 52. Cross-section B-B is perpendicular to cross-section A-Aand is along a row of the MRAM array 52 and in a direction of, forexample, a word line for the MRAM array 52. Subsequent figures refer tothese reference cross-sections for clarity. Specifically, FIGS. 12A,13A, and 14A are illustrated along cross-section A-A, and FIGS. 12B,13B, and 14B are illustrated along cross-section B-B.

In FIGS. 12A and 12B, the hard mask 152 is used as an etching mask topattern the IMD layer 150 and etch stop layer 148. The patterning mayinclude one or more etching processes, and forms openings 156 in the IMDlayer 150 and etch stop layer 148. As shown, the openings 156 havesubstantially the same top-down shape and dimensions (e.g., the samewidth W₁ and same length L₁) as the openings 154 in the hard mask 152(see FIG. 11 ). Specifically, a first etching process can be performedto form the openings 156 in the IMD layer 150, and a second etchingprocess can be performed to extend the openings 156 through the etchstop layer 148. In some embodiments, the patterning is one or more dryetching process(es), such as one or more anisotropic etchingprocess(es). The etch stop layer 148 helps protect the top electrodes136, and thus the MTJ stacks 134, from over-etching damage during theetching of the IMD layer 150. Because the width W₁ of the openings 156is greater than the diameter D₁ of the MRAM cells 58 (see FIG. 11 ), theopenings 156 expose sidewalls of the top electrodes 136 in thecross-section illustrated by FIG. 12B. In some embodiments, residualportions 148R of the etch stop layer 148 can remain between adjacent topelectrodes 136. Although the residual portions 148R of the etch stoplayer 148 can remain, top surfaces of the top electrodes 136 areexposed.

The openings 156 have several depths, as measured from the planartopmost surface of the IMD layer 150. The openings 156 have a depth D₃over the top electrodes 136, which can be in the range of about 100 Å toabout 300 Å. The openings 156 have a depth D₄ over the residual portions148R of the etch stop layer 148, which can be in the range of about 300Å to about 400 Å. In this embodiment, the openings 156 do not fullyexpose the top surfaces of all of the top electrodes 136. Rather, someof the top surfaces of the top electrodes 136 are only partiallyexposed. In other embodiments (discussed further below), the openings156 fully expose the top surfaces of all of the top electrodes 136.

In FIGS. 13A and 13B, a shared electrode layer 158 is formed on the hardmask 152 and in the openings 156 (see FIGS. 12A and 12B). The sharedelectrode layer 158 can be formed of a conductive material. In someembodiments, the shared electrode layer 158 is formed using similarmaterials and methods as the top electrode layer 120 (see FIG. 4 )and/or the hard mask 152, in embodiments where the hard mask 152comprises a conductive material. The shared electrode layer 158 can beformed to a thickness in the range of about 500 Å to about 800 Å.

In FIGS. 14A and 14B, a planarization process is performed to planarizethe shared electrode layer 158 and IMD layer 150. The planarizationprocess can be a CMP process, a mechanical grinding process, or thelike. The hard mask 152 and excess portions of the shared electrodelayer 158 outside of the openings 156 (see FIGS. 13A and 13B) areremoved by the planarization process. The planarization process formsshared electrodes 160, which comprise remaining portions of the sharedelectrode layer 158.

FIG. 15 is a top-down view of the MRAM device 50 after formation of theshared electrodes 160. As shown, the shared electrodes 160 havesubstantially the same top-down shape and dimensions (e.g., the samewidth W₁ and same length L₁) as the openings 154 in the hard mask 152(see FIG. 11 ). In this embodiment, the shared electrodes 160 fullyoverlap with MRAM cells 58 in the center regions of the sharedelectrodes 160, but only partially overlap with the MRAM cells 58 at theend regions of the shared electrodes 160.

In FIG. 16 , the IMD layer 150, etch stop layer 148, and IMD layer 108are patterned to expose the etch stop layer(s) 106 in the logic region50L. In some embodiments, the patterning process may comprise suitablephotolithography and etching processes. Portions of the IMD layer 150,etch stop layer 148, and IMD layer 108 in the memory region 50M remainafter the patterning process.

In FIG. 17 , some of the etch stop layer(s) 106 may optionally beremoved, such as in embodiments where the etch stop layer(s) 106comprise a multilayer. For example, when the etch stop layer(s) 106comprise a first etch stop layer 106A and a second etch stop layer 106B,portions of the second etch stop layer 106B in the logic region 50L canbe removed to expose the underlying first etch stop layer 106A. Thesecond etch stop layer 106B may be removed using an isotropic wet cleanprocess that is selective to the material of the second etch stop layer106B. The etching process used to remove the second etch stop layer 106Bmay be different from the etching process(es) used to pattern the IMDlayer 150, etch stop layer 148, and IMD layer 108 (e.g., differentetchants and/or other etching process parameters may be used). Usingmultilayered etch stop layer(s) 106 may be advantageous in someembodiments. For example, the second etch stop layer 106B can be etchedslower than the first etch stop layer 106A by the etching process(es)used to etch the IMD layer 150, etch stop layer 148, and IMD layer 108(see FIG. 16 ). Likewise, the first etch stop layer 106A can be etchedslower than the second etch stop layer 106B by one or more etchingprocess(es) that will be subsequently used to pattern openings forconductive features in the logic region 50L (see FIG. 21 ).

In FIG. 18 , an IMD layer 162 is formed on the shared electrodes 160,IMD layer 150, and first etch stop layer 106A. In some embodiments, theIMD layer 162 is formed using similar materials and methods as the IMDlayer 108. The IMD layer 162 can be formed to a thickness in the rangeof about 1100 Å to about 1650 Å. An anti-reflective layer 164 is thenformed on the IMD layer 162. The anti-reflective layer 164 may be anitrogen-free anti-reflective layer (NFARL), and can be formed of anitrogen-free dielectric material such as silicon oxycarbide. Theanti-reflective layer 164 can be formed to a thickness in the range ofabout 150 Å to about 400 Å. The anti-reflective layer 164 will be usedto protect the memory region 50M during subsequent processing of thelogic region 50L.

In FIG. 19 , openings 166 are formed in the logic region 50L, exposingthe conductive features 104 in the logic region 50L. Specifically, theopenings 166 are formed through the anti-reflective layer 164, IMD layer162, and first etch stop layer 106A. The openings 166 can be patternedby suitable photolithography and etching processes. Each of the openings166 has an upper (e.g., trench) portion, in which a conductive line willbe formed, and a lower (e.g., via) portion, in which a conductive viawill be formed. In some embodiments, the openings 166 are formed by avia-first process. In other embodiments, the openings 166 are formed bya trench-first process. As discussed further below, an etchback processcan optionally be performed to remove portions of the IMD layer 162 andanti-reflective layer 164 over the MRAM cells 58 before the openings 166are formed.

In FIG. 20 , a conductive material 168 is formed in the openings 166.The conductive material 168 may overfill the openings 166 and may alsobe formed over the IMD layer 162 and anti-reflective layer 164. Theconductive material 168 can be copper, aluminum, tungsten, gold,combinations thereof, or the like, and can be formed in the openings 166by an electro-chemical plating process, CVD, ALD, PVD, the like, or acombination thereof.

In FIG. 21 , a planarization process is performed to remove excess ofthe conductive material 168 outside of the openings 166. Theplanarization process can be a CMP process, a mechanical grindingprocess, or the like. The planarization process can remove theanti-reflective layer 164, and expose the topmost surfaces of the IMDlayer 150 and shared electrodes 160. The planarization process formsconductive features 170, which comprise remaining portions of theconductive material 168 in the openings 166. The conductive features 170include conductive vias 170V, which are formed in the lower (e.g., via)portions of the openings 166, and conductive lines 170L, which areformed in the upper (e.g., trench) portions of the openings 166. Thememory region 50M may be free from the conductive vias 170V andconductive lines 170L. Although each conductive via 170V andcorresponding conductive line 170L is illustrated as a separate element,it should be appreciated that they may be a continuous conductivefeature, such as in embodiments where they are formed by a dualdamascene process. After the planarization process, top surfaces of theconductive features 170, IMD layer 162, IMD layer 150, and sharedelectrodes 160 are planar.

After the planarization process, the shared electrodes 160 have severalheights, as measured from the planar topmost surface of the IMD layer150. The shared electrodes 160 have a height H₁ over the top electrodes136, which can be in the range of about 150 Å to about 250 Å. The sharedelectrodes 160 have a height H₂ over the residual portions 148R (seeFIG. 12A) of the etch stop layer 148, which can be in the range of about230 Å to about 350 Å.

In FIG. 22 , another metallization layer (e.g., M6, see FIG. 2 ) of theinterconnect structure is formed. The metallization layer comprises oneor more etch stop layer(s) 172, an IMD layer 174, and conductivefeatures 176. The conductive features include conductive vias 176V(which can correspond to the metal vias V6, see FIG. 2 ) and conductivelines 176L (which can correspond to the metal lines L6, see FIG. 2 ),and are formed in both the logic region 50L and memory region 50M. Insome embodiments, the etch stop layer(s) 172 can be formed using similarmaterials and methods as the etch stop layer(s) 106. In someembodiments, the IMD layer 174 is formed using similar materials andmethods as the IMD layer 162. In some embodiments, the conductive vias176V and conductive lines 176L are formed using similar materials andmethods as, respectively, the conductive vias 170V and conductive lines170L. Although each conductive via 176V and corresponding conductiveline 176L is illustrated as a separate element, it should be appreciatedthat they may be a continuous conductive feature, such as in embodimentswhere they are formed by a dual damascene process. Notably, theconductive vias 176V and conductive lines 176L may be formed of adifferent conductive material than the shared electrodes 160. Selectionof the various conductive materials allows the contact resistance to theshared electrodes 160 to be tuned. The conductive features 176 areelectrically connected to the memory devices (e.g., MRAMs) formed in thememory region 50M and the logic devices (e.g., logic circuits) formed inthe logic region 50L. Specifically, some of the conductive vias 176V arephysically and electrically connected to the shared electrodes 160. Insome embodiments, the conductive vias 176V and conductive lines 176Lelectrically connect the memory devices in the memory region 50M to thelogic devices in the logic region 50L. In some embodiments, theconductive features 176 in the logic region 50L and the memory region50M are formed in a same process. In some embodiments, the conductivefeatures 176 in the logic region 50L and the conductive features 176 inthe memory region 50M are formed in different processes. For example,because the shared electrodes 160 provide an increased landing area, theconductive features 176 in the memory region 50M may be formed larger(e.g., wider) than the conductive features 176 in the logic region 50L,which can help reduce the contact resistance to the MRAM cells 58.

FIG. 23 is a top-down cutaway view of the MRAM device 50 after formationof the conductive vias 176V and conductive lines 176L. As shown, theconductive lines 176L include bit lines BL for the MRAM array 52 (seeFIG. 1 ). Each bit line BL is electrically connected to multiple sharedelectrodes 160 by the conductive vias 176V. In turn, each of the sharedelectrodes 160 is electrically connected to multiple MRAM cells 58 (seeFIG. 15 ). The conductive vias 176V have a width W₂, which can be in therange of about 450 Å to about 650 Å. The widths W₁ of the sharedelectrodes 160 are greater than the widths W₂ of the conductive vias176V.

Embodiments may achieve advantages. The diameters D₁ of the MRAM cells58 (see FIG. 11 ) can be small. Specifically, the diameters D₁ of theMRAM cells 58 are smaller than the widths W₂ of the conductive vias176V, particularly when the MRAM cells 58 are formed in a higher level(e.g., M5 in FIG. 2 ) of an interconnect structure. However, the widthsW₁ of the shared electrodes 160 are greater than the widths W₂ of theconductive vias 176V. Advantageously, the shared electrodes 160 thusprovide landing pads of sufficient size for the conductive vias 176V,which can prevent punch-through to the underlying layers duringformation of the conductive vias 176V. For example, the top electrodes136 and MTJ stacks 134 can be protected from over-etching damage whenetching the openings for the conductive vias 176V. Further, by providinga larger contact area, the contact resistance of the conductive vias176V can be reduced. Finally, as noted above, the conductive materialselected for the shared electrodes 160 can be different from that ofoverlying conductive features 176, which allows the contact resistanceto the shared electrodes 160 to be tuned.

FIGS. 24 and 25 are various views of a MRAM device 50, in accordancewith some embodiments. FIG. 24 is shown at a similar stage ofmanufacturing as FIG. 15 , and FIG. 25 is shown at a similar stage ofmanufacturing as FIG. 22 . In this embodiment, the shared electrodes 160are formed to a greater length L₁ than the previous embodiment. Forexample, in this embodiment, the lengths L₁ can be in the range of about1500 Å to about 50 μm. As a result of their longer lengths L₁, theshared electrodes 160 do not partially overlap with the MRAM cells 58 atthe end regions of the shared electrodes 160. Rather, in thisembodiment, the shared electrodes 160 fully overlap with all of the MRAMcells 58 that the shared electrodes 160 are in contact with. Increasingthe contact area may allow the contact resistance to the MRAM cells 58to be further reduced.

FIGS. 26 through 40 are cross-sectional views of intermediate stages inthe manufacturing of an interconnect structure for the MRAM device 50,in accordance with some other embodiments. The interconnect structurealso includes a MRAM array of memory cells. As discussed further below,protective structures will be formed around the memory cells of the MRAMarray, which helps protect the memory cells during the subsequentformation of overlying metallization layers. Some features shown inFIGS. 26 through 40 are similar to features shown in FIGS. 3 through 23, and their descriptions are not repeated. Such features are shown usingsimilar reference numerals.

In FIG. 26 , an intermediate structure similar to that described withrespect to FIG. 6 is obtained. A passivation layer 202 is then blanketformed over the MRAM cells 58 and in the recesses 130 (see FIG. 6 ). Insome embodiments, the passivation layer 202 may comprise silicon oxide,silicon nitride, silicon oxynitride, silicon carbide, siliconcarbonitride, a combination thereof, or the like, and may be formedusing CVD, plasma-enhanced chemical vapor deposition (PECVD), ALD,plasma-enhanced atomic layer deposition (PEALD), PVD, a combinationthereof, or the like. In some embodiments, the passivation layer 202 isa nitride such as silicon nitride. The passivation layer 202 can reduceor prevent moisture (e.g., H₂O) diffusion into the MRAM cells 58 duringsubsequent processing. The passivation layer 202 is formed to athickness in the range of about 500 Å to about 15000 Å. Specifically,the passivation layer 202 is formed to a sufficient thickness to fillthe recesses 130 and bury the MRAM cells 58.

A dielectric layer 204 is then formed over the passivation layer 202. Insome embodiments, the dielectric layer 204 is formed using similarmaterials and methods as the IMD layer 108. For example, the dielectriclayer 204 can be formed of an oxide, such as silicon oxide. Thedielectric layer 204 can be formed to a thickness in the range of about100 Å to about 300 Å.

A planarization stop layer 206 is then formed on the dielectric layer204. The planarization stop layer 206 may be a nitrogen-free layer, andmay be formed of a nitrogen-free dielectric material. For example, theplanarization stop layer 206 can be formed of a doped or undoped oxide,such as silicon oxycarbide. The planarization stop layer 206 can beformed to a thickness in the range of about 80 Å to about 150 Å. Theplanarization stop layer 206 will be used to protect the logic region50L during subsequent processing (discussed further below).

A dielectric layer 208 is then formed over the planarization stop layer206. In some embodiments, the dielectric layer 208 is formed usingsimilar materials and methods as the IMD layer 108 and dielectric layer204. For example, the dielectric layer 208 can be formed of siliconoxide. The dielectric layer 208 can be formed to a thickness in therange of about 200 Å to about 400 Å.

A coating layer 210 is then formed over the dielectric layer 208. Thecoating layer 210 acts as a buffer layer to help reduce topographyvariations during a subsequent etchback process. The coating layer 210can be formed using a coating process, such as a spin coating process.The coating layer 210 can be formed of a material that is ashable andfluid, such as a bottom layer of photoresist. After the spin coatingprocess, the material can be cured. Curing the material hardens thecoating layer 210. In some embodiments, curing the material comprisesexposing the material to an elevated temperature.

In FIG. 27 , an etchback process is performed to remove portions of thecoating layer 210, dielectric layer 208, and planarization stop layer206. Specifically, the etchback process removes portions of theplanarization stop layer 206 in the memory region 50M to expose portionsof the dielectric layer 204 over the MRAM cells 58. The logic region 50Lis covered by remaining portions of the planarization stop layer 206.The etchback process may be a dry etching process, using an etchant suchas CH_(x)F_(y), CF₄, He, O₂, N₂, Ar, NF₃, SF₆, combinations thereof, orthe like as an etching gas. The coating layer 210 can be consumed by theetchback process, or the coating layer 210 can be removed after theetchback process by, e.g., a suitable ashing or stripping process. Insome embodiments, some portions of the coating layer 210 remain in thelogic region 50L after the etchback process, and those portions areremoved after the etchback process.

In FIG. 28 , a planarization process is performed to expose the topelectrodes 136 of the MRAM cells 58. The planarization process can be aCMP process, a mechanical grinding process, or the like. Theplanarization process removes remaining portions of the dielectric layer208 and also removes portions of the dielectric layer 204 over the MRAMcells 58. The planarization stop layer 206 has a lower removal rate thanthe dielectric layers 204 and 208, relative to the planarizationprocess. As such, the planarization process can be performed until theplanarization stop layer 206 (and thus the top electrodes 136) isexposed. In some embodiments, the topmost surface of the planarizationstop layer 206 is formed to a sufficient thickness such that it extendsabove the topmost surfaces of the top electrodes 136, and the topelectrodes 136 are exposed by, e.g., dishing that can occur during theplanarization process. The exposed portions of the planarization stoplayer 206 cover the logic region 50L, and can cover a portion of thememory region 50M. Although the planarization process does not removethe planarization stop layer 206, it can reduce the thickness of theplanarization stop layer 206. After the planarization process, theplanarization stop layer 206 can have a thickness T₁ in the range ofabout 50 Å to about 100 Å.

In FIG. 29 , an etchback process 212 is performed to recess thepassivation layer 202 and form recesses 214 around the top electrodes136 of the MRAM cells 58. The recesses 214 are formed to a depth D₅,which can in the range of about 50 Å to about 200 Å. The recesses 214expose the sidewalls of the top electrodes 136, but do not expose thesidewalls of the MTJ stacks 134. The sidewalls of the MTJ stacks 134remain covered and protected by the passivation layer 202 after theetchback process 212.

The etchback process 212 is selective to the material of the passivationlayer 202. As noted above, in some embodiments, the passivation layer202 is a nitride, and the dielectric layer 204 and planarization stoplayer 206 are oxides. In such embodiments, the etchback process 212 canetch the material of the passivation layer 202 (e.g., nitrides) at ahigher rate than the material(s) of the dielectric layer 204 andplanarization stop layer 206 (e.g., oxides). For example, the ratio ofthe etch rate of the passivation layer 202 to the etch rates of thedielectric layer 204 and planarization stop layer 206, relative to theetchback process 212, can be in the range of about 3:1 to about 10:1. Asan example of the etchback process 212, a dry etching process such asIBE, Reactive Ion Etching (RIE), or the like can be performed using anetchant such as HBr, CF₄, He, O₂, N₂, CH_(x)F_(y), combinations thereof,or the like as an etching gas. N₂, Ar, He, combinations thereof, or thelike may be used as carrier gases for the etching gas. The etching maybe implemented using glow discharge plasma (GDP), capacitive coupledplasma (CCP), inductively coupled plasma (ICP), or the like. The etchingcan be performed with a source power in the range of about 100 watts andabout 1500 watts, and can be performed with a bias voltage of up toabout 1000 volts. The etching can be performed for a duration in therange of about 7 seconds and about 300 seconds. Performing the etchbackprocess 212 with such parameters allows for a high etch selectivitybetween the material of the passivation layer 202 (e.g., nitrides) andthe material(s) of the dielectric layer 204 and planarization stop layer206 (e.g., oxides).

Although the etchback process 212 is selective to the material of thepassivation layer 202, some etching of the planarization stop layer 206can still occur. For example, the etchback process 212 can reduce thethickness of the planarization stop layer 206 to a thickness T₂ in therange of about 10 Å to about 50 Å. The new thickness T₂ of theplanarization stop layer 206 is smaller than the original thickness T₁of the planarization stop layer 206, but is still of sufficientthickness to withstand subsequent processing. In some embodiments, thenew thickness T₂ of the planarization stop layer 206 is at least half ofthe original thickness T₁ of the planarization stop layer 206.

In FIG. 30 , a protection layer 216 is formed in the recesses 214, andon exposed surfaces of the MRAM cells 58, dielectric layer 204, andplanarization stop layer 206. The protection layer 216 is formed of adielectric material such as aluminum nitride, aluminum oxide, siliconcarbide, silicon carbonitride, a combination thereof, multilayersthereof, or the like, and is formed by a deposition process such asphysical vapor deposition (PVD), chemical vapor deposition (CVD), ALD,combinations thereof, or the like. The protection layer 216 is formed ofa material that has a high selectivity relative an etching process thatwill be used to pattern subsequently formed metallization layers of theinterconnect structure (discussed further below). For example, theprotection layer 216 can be a silicon carbide layer, an aluminum oxidelayer, or a multilayer comprising a silicon carbide sub-layer and analuminum oxide sub-layer on the silicon carbide sub-layer. Afterformation, the protection layer 216 surrounds the top electrodes 136 ofthe MRAM cells 58. Advantageously, forming the protection layer 216 inthe recesses 214 allows the protection layer 216 to be self-aligned tothe top electrodes 136.

In FIG. 31 , a planarization process is performed to expose the topelectrodes 136 of the MRAM cells 58. The planarization process removesportions of the protection layer 216 outside of the recesses 214 (seeFIG. 29 ), e.g., portions of the protection layer 216 over the MRAMcells 58, dielectric layer 204, and planarization stop layer 206. Theplanarization process can be a CMP process, a mechanical grindingprocess, or the like. The planarization stop layer 206 has a lowerremoval rate than the protection layer 216, relative to theplanarization process. As such, the planarization process can beperformed until the planarization stop layer 206 is exposed. The topelectrodes 136 are exposed after the planarization process. Theplanarization process forms protective structures 218, which comprisethe portions of the protection layer 216 remaining in the recesses 214after the planarization process.

Multiple planarization processes are performed using the planarizationstop layer 206. Specifically, the planarization process of FIG. 28 andFIG. 31 are both performed, and both are stopped on the planarizationstop layer 206. Performing multiple planarization processes helps reduceuneven topography that can be caused by pattern density variationsbetween the logic region 50L and memory region 50M, helping ensure thefeatures in the logic region 50L and the memory region 50M share aplanar top surface.

After the planarization process, the protective structures 218 have athickness T₃, which can be in the range of about 80 Å to about 200 Å,and the top electrodes 136 have a thickness T₄, which can be in therange of about 150 Å to about 300 Å. The thickness T₃ is less than thethickness T₄. Specifically, the thickness T₃ of the protectivestructures 218 is sufficient to ensure the MRAM cells 58 are protectedin subsequent processing, but small enough to ensure the sidewalls ofthe MTJ stacks 134 are free from undesired materials (thus retainingtheir desired high resistance (R_(ap)) and a low resistance (R_(p))values), such as residue from a subsequent contact etch process(discussed further below).

In FIG. 32 , an anti-reflective layer 220 is formed on the planarizedsurface of the intermediate structure. Specifically, the anti-reflectivelayer 220 is formed on planarized surfaces of the protective structures218, top electrodes 136, planarization stop layer 206, and dielectriclayer 204. The anti-reflective layer 220 may be a nitrogen-freeanti-reflective layer (NFARL), and can be formed of a nitrogen-freedielectric material such as silicon oxycarbide. In some embodiments, theanti-reflective layer 220 is formed of a different material than theprotective structures 218. The anti-reflective layer 220 can be formedto a thickness in the range of about 100 Å to about 350 Å. Theanti-reflective layer 220 will be used to protect the memory region 50Mduring subsequent processing of the logic region 50L.

In FIG. 33 , the intermediate structure is patterned to expose the etchstop layer(s) 106 in the logic region 50L. The patterning can comprisesuitable photolithography and etching processes. For example, one ormore dry etching process(es) can be performed using an etching mask 222to etch the anti-reflective layer 220, planarization stop layer 206,dielectric layer 204, passivation layer 202, and IMD layer 108. Theetching mask 222 may be a photoresist, such as a single-layerphotoresist, a bi-layer photoresist, a tri-layer photoresist, or thelike. In some embodiments, the remaining portions of the planarizationstop layer 206 are removed by the etching process(es). In someembodiments (discussed below), portions of the planarization stop layer206 can remain after the etching process(es). Some portions of thedielectric layer 204 can remain in the memory region 50M after theetching process(es). The etching process(es) forms one or moreopening(s) 224 exposing the etch stop layer(s) 106, such as the secondetch stop layer 106B in embodiments where the etch stop layer(s) 106comprise a multilayer. The etching mask 222 can be consumed by theetching process(es), or the etching mask 222 can be removed after theetching process(es) by, e.g., a suitable ashing or stripping process.

In FIG. 34 , some of the etch stop layer(s) 106 may optionally beremoved, such as in embodiments where the etch stop layer(s) 106comprise a multilayer. For example, when the etch stop layer(s) 106comprise a first etch stop layer 106A and a second etch stop layer 106B,portions of the second etch stop layer 106B in the opening(s) 224 can beremoved to expose the underlying first etch stop layer 106A. The secondetch stop layer 106B may be removed using an isotropic wet clean processthat is selective to the material of the second etch stop layer 106B.The etching process used to remove the second etch stop layer 106B maybe different from the etching process(es) used to initially form theopening(s) 224 (e.g., different etchants and/or other etching processparameters may be used). Using multilayered etch stop layer(s) 106 maybe advantageous in some embodiments. For example, the second etch stoplayer 106B can be etched slower than the first etch stop layer 106A bythe etching process(es) used to etch the anti-reflective layer 220,planarization stop layer 206, dielectric layer 204, passivation layer202, and IMD layer 108 (see FIG. 32 ). Likewise, the first etch stoplayer 106A can be etched slower than the second etch stop layer 106B byone or more etching process(es) that will be subsequently used topattern openings for conductive features in the logic region 50L (seeFIG. 39 ).

In FIG. 35 , the IMD layer 162 is formed in the opening(s) 224 and overthe MRAM cells 58 and protective structures 218, such as on theanti-reflective layer 220. The anti-reflective layer 164 is then formedon the IMD layer 162. The anti-reflective layer 164 will be used toprotect the memory region 50M during subsequent processing of the logicregion 50L.

In FIG. 36 , an etchback process can optionally be performed to removeportions of the IMD layer 162 and anti-reflective layer 164 over theMRAM cells 58, thus exposing the anti-reflective layer 220. Portions ofthe logic region 50L, such as portions over the conductive features 104,can be covered by an etching mask 226 during the etchback process. Theetchback process may be a dry etching process, using an etchant such asCH_(x)F_(y), CF₄, He, O₂, N₂, Ar, NF₃, SF₆, combinations thereof, or thelike as an etching gas. The etching mask 226 can be consumed by theetchback process, or the etching mask 226 can be removed after theetchback process by, e.g., a suitable ashing or stripping process. Afterthe etchback process, the remaining portions of the anti-reflectivelayer 164 are disposed in the logic region 50L, and do not extend intothe memory region 50M. In some embodiments, the etchback process isomitted, and the portions of the IMD layer 162 and anti-reflective layer164 over the MRAM cells 58 can be removed during a subsequentplanarization process (discussed further below).

In FIG. 37 , the openings 166 are formed in the logic region 50L,exposing the conductive features 104 in the logic region 50L.Specifically, the openings 166 are formed through the anti-reflectivelayer 164, IMD layer 162, and any of the etch stop layer(s) 106 (e.g.,the first etch stop layer 106A) remaining in the logic region 50L. Theopenings 166 can be formed using similar processes and materials asthose discussed above with respect to FIG. 19 .

In FIG. 38 , the conductive material 168 is formed in the openings 166.The conductive material 168 may overfill the openings 166 and may alsobe formed over the IMD layer 162 and anti-reflective layers 164 and 220.The conductive material 168 can be formed using similar processes andmaterials as those discussed above with respect to FIG. 20 .

In FIG. 39 , a planarization process is performed to remove excess ofthe conductive material 168 outside of the openings 166. Theplanarization process can be a CMP process, a mechanical grindingprocess, or the like. The planarization process can remove theanti-reflective layers 164 and 220, and expose the top electrodes 136and protective structures 218. The planarization process forms theconductive features 170. After the planarization process, top surfacesof the conductive features 170, IMD layer 162, protective structures218, dielectric layer 204, and top electrodes 136 are planar.

As noted above, the etchback process shown in FIG. 36 is optional. Theetchback process can help reduce uneven topography that can be caused bypattern density variations between the logic region 50L and memoryregion 50M. In some embodiments, the etchback process shown in FIG. 36is omitted, and the portions of the IMD layer 162 and anti-reflectivelayer 164 over the MRAM cells 58 can instead be removed during theplanarization process shown in FIG. 39 .

In FIG. 40 , the etch stop layer(s) 172, IMD layer 174, and conductivefeatures 176 are formed. In the illustrated embodiment, the etch stoplayer(s) 172 comprise a single etch stop layer 172, such as a layer ofsilicon nitride. The conductive vias 176V in the memory region 50M arephysically and electrically connected to the top electrodes 136. TheMRAM cells 58 can be small, particularly when high-density memories aredesired. For example, the diameters D₁ of the top electrodes 136 can besmaller than the width W₂ of the overlying conductive vias 176V,particularly when the MRAM cells 58 are formed in a higher level (e.g.,M5 in FIG. 2 ) of an interconnect structure. As such, the conductivevias 176V can contact the top electrodes 136 and portions of theprotective structures 218.

In some embodiments, the conductive features 176 are formed usingsimilar materials and methods as the conductive features 170. Forexample, openings are formed exposing the conductive features 170 andtop electrodes 136. The openings are filled with a conductive material,and a planarization process is then performed to form the conductivefeatures 176, which comprise remaining portions of the conductivematerial in the openings. When forming the openings for the conductivefeatures 176, the IMD layer 174 is patterned with a first etchingprocess, and the etch stop layer 172 is used to stop the first etchingprocess. The first etching process can comprise suitablephotolithography and etching steps. The etch stop layer 172 is thenopened with a second etching process to expose the conductive features170 and top electrodes 136. The second etching process can comprisesuitable photolithography and etching steps. The protective structures218 surround and protect the MRAM cells 58 during the second etchingprocess. Protection may be accomplished in several manners. Theprotective structures 218 prevent the second etching process frometching the MTJ stacks 134 of the MRAM cells 58. Damage to the MRAMcells 58 may thus be avoided.

In some embodiments, the protective structures 218 are formed of asimilar etch stop material as the etch stop layer 172. The amount ofetch stop material protecting the MRAM cells 58 is thus increased,enlarging the processing window for the second etching process. Thelikelihood of etching the MTJ stacks 134 is thus decreased.

In some embodiments, the protective structures 218 are formed of adifferent etch stop material than the etch stop layer 172. Specifically,the second etching process can be selective to the material of the etchstop layer 172. For example, in some embodiments, the protectivestructures 218 are silicon carbide and/or aluminum oxide, and the etchstop layer 172 is silicon nitride. In such embodiments, the secondetching process can etch the material of the etch stop layer 172 (e.g.,silicon nitride) at a higher rate than the material of the protectivestructures 218 (e.g., silicon carbide and/or aluminum oxide). Forexample, the ratio of the etch rate of the etch stop layer 172 to theetch rate of the protective structures 218, relative to the secondetching process, can be in the range of about 1 to about 5. As anexample of the second etching process, an isotropic wet clean processthat is selective to the material of the etch stop layer 172 can beperformed. The etching can be performed with a solution that includeswater, such as deionized water, carbonated deionized water, or the like.The etching can be performed for a duration in the range of about 5seconds and about 600 seconds. Performing the second etching processwith such parameters allows for a high etch selectivity between thematerial of the etch stop layer 172 (e.g., silicon nitride) and thematerial of the protective structures 218 (e.g., silicon carbide and/oraluminum oxide). The likelihood of etching the MTJ stacks 134 is thusfurther decreased.

FIG. 41 is a cross-sectional view of the MRAM device 50, in accordancewith some other embodiments. FIG. 41 shows an embodiment where someetching of the protective structures 218 occurs during formation of aconductive feature 176. As shown, the protective structures 218 helpprotect the MTJ stacks 134 even when partial punch-through of theprotective structures 218 occurs.

FIG. 42 is a cross-sectional view of the MRAM device 50, in accordancewith some other embodiments. In this embodiment, portions of theplanarization stop layer 206 remain after the etching process(es) ofFIG. 33 . Such remaining portions of the planarization stop layer 206are disposed between the etch stop layer 172 and the remaining portionsof the dielectric layer 204.

Embodiments may achieve advantages. Forming the protective structures218 around the top electrodes 136 helps protect the MRAM cells 58 whenforming the overlying metallization layer. Specifically, etching of theMTJ stacks 134 can be avoided during formation of the conductivefeatures 176. The protective structures 218 can protect the topelectrodes 136 by either enlarging the processing window for forming theconductive features 176, or acting as an etch stop layer to preventetching of the MTJ stacks 134. Damage to the MRAM cells 58 may thus beavoided, increasing manufacturing yield of the resulting devices.

Although embodiments have been described in the context of MRAM cells,it should be appreciated that similar techniques may be used in formingother types of memory cells with programmable resistance elements. Forexample, similar techniques may be used in forming phase-change memory(PCRAM) cells, resistive random-access memory (RRAM) cells, and thelike.

In an embodiment, a device includes: a magnetoresistive random accessmemory (MRAM) array including MRAM cells arranged in rows and columns,where a first column of the columns includes: first bottom electrodesarranged along the first column; first magnetic tunnel junction (MTJ)stacks over the first bottom electrodes; a first shared electrode overeach of the first MTJ stacks; second bottom electrodes arranged alongthe first column; second MTJ stacks over the second bottom electrodes; asecond shared electrode over each of the second MTJ stacks; and a bitline electrically connected to the first shared electrode and the secondshared electrode.

In some embodiments of the device, the first bottom electrodes, thesecond bottom electrodes, the first shared electrode, and the secondshared electrode each include titanium nitride, and the bit lineincludes copper. In some embodiments of the device, the first columnfurther includes: first top electrodes disposed between the first MTJstacks and the first shared electrode; second top electrodes disposedbetween the second MTJ stacks and the second shared electrode; a firstconductive via physically and electrically connecting the bit line tothe first shared electrode; and a second conductive via physically andelectrically connecting the bit line to the second shared electrode,widths of the first conductive via and the second conductive via beinggreater than widths of each of the first top electrodes and each of thesecond top electrodes. In some embodiments of the device, widths of thefirst shared electrode and the second shared electrode are greater thanthe widths of the first top electrodes, the second top electrodes, thefirst conductive via, and the second conductive via. In some embodimentsof the device, the first shared electrode fully overlaps with each ofthe first top electrodes. In some embodiments of the device, the firstshared electrode fully overlaps with a first subset of the first topelectrodes, and partially overlaps with a second subset of the first topelectrodes. In some embodiments of the device, the first sharedelectrode and the second shared electrode have the same length along thefirst column. In some embodiments of the device, each row of the rowsincludes a word line electrically connected to one of the first bottomelectrodes or the second bottom electrodes, and further including: a rowdecoder electrically connected to the word line of each of the rows; anda column decoder electrically connected to the bit line. In someembodiments of the device, the first column further includes: a firstspacer laterally surrounding the first bottom electrodes and the firstMTJ stacks; an etch stop layer extending along top surfaces andsidewalls of the first spacer; and a first inter-metal dielectric (IMD)layer on the etch stop layer, where the first shared electrode extendsthrough the first IMD layer and the etch stop layer. In some embodimentsof the device, the etch stop layer includes aluminum nitride.

In an embodiment, a method includes: forming a first inter-metaldielectric (IMD) layer over a substrate; forming a bottom electrodelayer over the first IMD layer; forming a magnetic tunnel junction (MTJ)film stack over the bottom electrode layer; forming a top electrodelayer over the MTJ film stack; patterning the top electrode layer, theMTJ film stack, and the bottom electrode layer to form a firstmagnetoresistive random access memory (MRAM) cell and a second MRAMcell; forming a spacer around sidewalls of the first MRAM cell and thesecond MRAM cell; depositing an etch stop layer over the spacer andexposed portions of the first IMD layer; depositing a second IMD layerover the etch stop layer; exposing portions of the first MRAM cell andthe second MRAM cell; and forming a shared electrode on the exposedportions of the first MRAM cell and the second MRAM cell.

In some embodiments of the method, exposing the portions of the firstMRAM cell and the second MRAM cell includes etching an opening in thesecond IMD layer, and forming the shared electrode includes: depositinga conductive material in the opening; and planarizing the conductivematerial to remove portions of the conductive material outside of theopening, the shared electrode including remaining portions of theconductive material after the planarizing. In some embodiments, themethod further includes: depositing a third IMD layer over the sharedelectrode and the second IMD layer; planarizing the third IMD layer suchthat surfaces of the third IMD layer, the second IMD layer, and theshared electrode are planar; and forming conductive features in thethird IMD layer. In some embodiments, the method further includes:depositing a fourth IMD layer over the third IMD layer, the second IMDlayer, and the shared electrode; forming a conductive via in the fourthIMD layer; and forming a bit line in the fourth IMD layer, theconductive via electrically and physically connecting the bit line tothe shared electrode. In some embodiments of the method, exposing theportions of the first MRAM cell and the second MRAM cell includesetching an opening in the second IMD layer and the etch stop layer, theopening fully exposing a first top surface of the first MRAM cell andpartially exposing a second top surface of the second MRAM cell. In someembodiments of the method, exposing the portions of the first MRAM celland the second MRAM cell includes etching an opening in the second IMDlayer and the etch stop layer, the opening fully exposing a first topsurface of the first MRAM cell and a second top surface of the secondMRAM cell.

In an embodiment, a method includes: forming a magnetoresistive randomaccess memory (MRAM) cell over a substrate, the MRAM cell including: afirst bottom electrode over the substrate; a first magnetic tunneljunction (MTJ) stack over the first bottom electrode; a first topelectrode over the first MTJ stack; forming a first dielectric layerlaterally surrounding the first bottom electrode, the first MTJ stack,and the first top electrode; recessing the first dielectric layer toexpose portions of sidewalls of the first top electrode; forming aprotective structure contacting the exposed portions of the sidewalls ofthe first top electrode; depositing a first inter-metal dielectric (IMD)layer over the MRAM cell; and forming a conductive feature extendingthrough the first IMD layer, the conductive feature contacting the firsttop electrode and the protective structure.

In some embodiments of the method, recessing the first dielectric layerforms a recess, and forming the protective structure includes:depositing a second dielectric layer in the recess; and planarizing thesecond dielectric layer to form the protective structure, surfaces ofthe protective structure and the first top electrode being planar. Insome embodiments, the method further includes: forming an etch stoplayer over the protective structure, the first IMD layer being depositedover the etch stop layer, the etch stop layer and the protectivestructure including different dielectric materials. In some embodiments,the method further includes: forming an etch stop layer over theprotective structure, the first IMD layer being deposited over the etchstop layer, the etch stop layer and the protective structure includingthe same dielectric material.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A device comprising: a magnetoresistive randomaccess memory array comprising magnetoresistive random access memorycells arranged in rows and columns, wherein a first column of thecolumns comprises: first bottom electrodes arranged along the firstcolumn; first magnetic tunnel junction stacks over the first bottomelectrodes; a first shared electrode over each of the first magnetictunnel junction stacks; second bottom electrodes arranged along thefirst column; second magnetic tunnel junction stacks over the secondbottom electrodes; a second shared electrode over each of the secondmagnetic tunnel junction stacks; and a bit line electrically connectedto the first shared electrode and the second shared electrode.
 2. Thedevice of claim 1, wherein the first bottom electrodes, the secondbottom electrodes, the first shared electrode, and the second sharedelectrode each comprise titanium nitride, and wherein the bit linecomprises copper.
 3. The device of claim 1, wherein the first columnfurther comprises: first top electrodes disposed between the firstmagnetic tunnel junction stacks and the first shared electrode; secondtop electrodes disposed between the second magnetic tunnel junctionstacks and the second shared electrode; a first conductive viaphysically and electrically connecting the bit line to the first sharedelectrode; and a second conductive via physically and electricallyconnecting the bit line to the second shared electrode, widths of thefirst conductive via and the second conductive via being greater thanwidths of each of the first top electrodes and each of the second topelectrodes.
 4. The device of claim 3, wherein widths of the first sharedelectrode and the second shared electrode are greater than the widths ofthe first top electrodes, the second top electrodes, the firstconductive via, and the second conductive via.
 5. The device of claim 3,wherein the first shared electrode fully overlaps with each of the firsttop electrodes.
 6. The device of claim 3, wherein the first sharedelectrode fully overlaps with a first subset of the first topelectrodes, and partially overlaps with a second subset of the first topelectrodes.
 7. The device of claim 1, wherein the first shared electrodeand the second shared electrode have the same length along the firstcolumn.
 8. The device of claim 1, wherein each row of the rows comprisesa word line electrically connected to one of the first bottom electrodesor the second bottom electrodes, and further comprising: a row decoderelectrically connected to the word line of each of the rows; and acolumn decoder electrically connected to the bit line.
 9. The device ofclaim 1, wherein the first column further comprises: a first spacerlaterally surrounding the first bottom electrodes and the first magnetictunnel junction stacks; an etch stop layer extending along top surfacesand sidewalls of the first spacer; and a first inter-metal dielectric onthe etch stop layer, wherein the first shared electrode extends throughthe first inter-metal dielectric and the etch stop layer.
 10. The deviceof claim 9, wherein the etch stop layer comprises aluminum nitride. 11.A device comprising: a first magnetoresistive random access memory cellcomprising a first top electrode; a second magnetoresistive randomaccess memory cell comprising a second top electrode; a firstinter-metal dielectric over the first magnetoresistive random accessmemory cell and the second magnetoresistive random access memory cell; ashared electrode in the first inter-metal dielectric, the sharedelectrode contacting the first top electrode and the second topelectrode, a top surface of the shared electrode being coplanar with atop surface of the first inter-metal dielectric; a second inter-metaldielectric over the shared electrode and the first inter-metaldielectric; and a bit line interconnect in the second inter-metaldielectric, the bit line interconnect contacting the shared electrode.12. The device of claim 11, wherein the first magnetoresistive randomaccess memory cell further comprises a first bottom electrode, thesecond magnetoresistive random access memory cell further comprises asecond bottom electrode, each of the first top electrode, the second topelectrode, the first bottom electrode, and the second bottom electrodecomprise a first conductive material, and the bit line interconnectcomprises a second conductive material.
 13. The device of claim 12,further comprising: a third inter-metal dielectric; a first word line inthe third inter-metal dielectric, the first word line connected to thefirst bottom electrode; and a second word line in the third inter-metaldielectric, the second word line connected to the second bottomelectrode.
 14. The device of claim 11, wherein a width of the sharedelectrode is greater than a diameter of the first top electrode and adiameter of the second top electrode.
 15. The device of claim 11,wherein the shared electrode fully overlaps the first top electrode andpartially overlaps the second top electrode.
 16. The device of claim 11,wherein the shared electrode fully overlaps the first top electrode andfully overlaps the second top electrode.
 17. A method comprising:forming a magnetoresistive random access memory cell over a substrate,the magnetoresistive random access memory cell comprising: a firstbottom electrode over the substrate; a first magnetic tunnel junctionstack over the first bottom electrode; a first top electrode over thefirst magnetic tunnel junction stack; forming a first dielectric layerlaterally surrounding the first bottom electrode, the first magnetictunnel junction stack, and the first top electrode; recessing the firstdielectric layer to expose portions of sidewalls of the first topelectrode; forming a protective structure contacting the exposedportions of the sidewalls of the first top electrode; depositing a firstinter-metal dielectric over the magnetoresistive random access memorycell; and forming a conductive feature extending through the firstinter-metal dielectric, the conductive feature contacting the first topelectrode and the protective structure.
 18. The method of claim 17,wherein recessing the first dielectric layer forms a recess, and whereinforming the protective structure comprises: depositing a seconddielectric layer in the recess; and planarizing the second dielectriclayer to form the protective structure, surfaces of the protectivestructure and the first top electrode being planar.
 19. The method ofclaim 17, further comprising: forming an etch stop layer over theprotective structure, the first inter-metal dielectric being depositedover the etch stop layer, the etch stop layer and the protectivestructure comprising the same dielectric material.
 20. The method ofclaim 17, further comprising: forming an etch stop layer over theprotective structure, the first inter-metal dielectric being depositedover the etch stop layer, the etch stop layer comprising siliconnitride, the protective structure comprising silicon carbide or aluminumoxide.